Use of cold flow improver compositions for fuels, blends thereof with biofuels and formulations thereof

ABSTRACT

The present invention relates to the use of polyalkyl(meth)acrylates as an additive to fuels, especially middle distillate fuels and blends thereof. The present invention further relates to the use of a composition comprising polyalkyl(meth)acrylates as dispersing species susceptible to disperse waxes and sludgy material at low temperatures and a hydrocarbon solvent/an oil for improving the cold flow properties of fuel oil and fuel oil compositions. The present invention further relates to the use of these compositions as an additive to fuels, especially in the function of paraffin dispersant, to such fuels themselves and to fuel additive concentrates which comprise this composition dissolved in a hydrocarbon solvent or an oil.

The present invention relates to the use of polyalkyl(meth)acrylates asan additive to fuels, especially middle distillate fuels and blendsthereof. The present invention further relates to the use of acomposition comprising polyalkyl(meth)acrylates as dispersing speciessusceptible to disperse waxes and sludgy material at low temperaturesand a hydrocarbon solvent or an oil for improving the cold flowproperties of fuel oil and fuel oil compositions.

The present invention further relates to the use of these compositionsas an additive to fuels, especially in the function of paraffindispersant, to such fuels themselves and to fuel additive concentrateswhich comprise this composition dissolved in a hydrocarbon solvent or anoil.

Fuels are nowadays typically obtained from fossil sources. However,these resources are limited, so that replacements are being sought.Therefore, interest is rising in renewable raw materials which can beused to produce fuels. A very interesting replacement is in particularbiodiesel fuel.

The term biodiesel is in many cases understood to mean a mixture offatty acid esters, usually fatty acid methyl esters (FAMEs), with chainlengths of the fatty acid fraction of 14 to 24 carbon atoms with 0 to 3double bonds. The higher the carbon number and the fewer double bondsare present, the higher is the melting point of the FAME. Typical rawmaterials are vegetable oils (i.e. glycerides) such as rapeseed oils,sunflower oils, soya oils, palm oils, coconut oils and, in isolatedcases, even used vegetable oils. These are converted to thecorresponding FAMEs by transesterification, usually with methanol underbasic catalysis.

The FAME content also affects the cold flow properties of the feedstock.The lower the carbon number and the lower the degree of saturation is inthe fatty acid chains, the better is the cold flow property of thefeedstock. The common methods to evaluate the cold flow quality are:pour point (PP) test as mentioned in ASTM D97, filterability limit viacold filter plugging point (CFPP) test measured to DIN EN 116 or ASTMD6371, and cloud point (CP) test as described in ASTM D2500.

Currently rapeseed oil methyl ester (RME) is the preferred stock forbiodiesel production in Europe as rapeseed allows producing biodieselfuel with relatively good cold flow properties. However with the highprice level of RME, mixtures of RME with other feedstock, such assoybean (SME) or palm methyl ester (PME), have been exploited as well.Soybean is the preferred feedstock in the Americas and palm oil ispreferred in Asia. In addition to the utilization of 100% biodiesel,mixtures with fossil diesel, i.e. the middle distillate of crude oildistillation, and biodiesel are also of interest owing to the improvedlow-temperature properties and better combustion characteristics.

In view of the declining ecological quality and decreasing world crudeoil reserves, the use of pure biodiesel (B100) has been an importanttarget in many countries. However, many issues, ranging from differentcombustion characteristics to corrosion of seal materials, have beenreported as hindrances to the use of biodiesel as a replacement forfossil diesel.

Middle distillate fuels of fossil origin, especially gas oils, dieseloils or extra light heating oils, which are obtained from mineral oil,have different composition depending on the origin of the crude oil andthe refinery process.

It has long been known that suitable additives can modify the crystalgrowth of the n-paraffins in middle distillate fuels. Very effectiveadditives prevent middle distillate fuels from becoming solid even attemperatures a few degrees Celsius below the temperature at which thefirst paraffin crystals crystallize out. Instead, fine, readilycrystallizing, separate paraffin crystals are formed which pass throughfilters in motor vehicles and heating systems or at least form a filtercake which is permeable to the liquid portion of the middle distillates,so that disruption-free operation is ensured.

The effectiveness of the cold flow improvers is expressed in accordanceto European Standard EN 116 indirectly by measuring the cold filterplugging point (CFPP).

Ethylene-vinyl carboxylate copolymers have been used for some time ascold flow improvers (CFI) or middle distillate flow improvers (MDFI).One disadvantage of these additives is that the precipitated paraffincrystals, owing to their higher density compared to the liquid portion,tend to settle out more and more at the bottom of the vessel in thecourse of storage. As a result, a homogenous low-paraffin phase forms inthe upper part of the vessel and a biphasic paraffin-rich layer at thebottom.

Since the fuel is usually drawn off just above the vessel bottom both infuel tanks and in storage or supply tanks of mineral oil dealers, thereis a risk that the high concentration of solid n-paraffins leads toplugging of filters and metering devices. The further the storagetemperature is below the precipitation temperature of the paraffins andthe longer storage times at such temperature are the greater this riskbecomes, since the amount of precipitated paraffin increases withfalling temperature. In particular, fractions of biodiesel might alsoenhance this undesired tendency of the middle distillate fuel ton-paraffin sedimentation.

The afore mentioned problems can be reduced significantly by virtue ofthe additional use of paraffin dispersants or wax anti-settlingadditives (WASA).

As the temperature of the fuel is reduced to below the cloud point, e.g.to the cold filter plugging point, small particles appear in the fuel,which tend to agglomerate and precipitate as large, plate-like orspherulites of wax. These wax crystals increase the difficulties totransport the fuel through lines and pumps and tend to plug fuel lines,screens and filters. The wax from a diesel fuel is primarily an n-alkanewax, crystallizes as platelets whereas the wax coming from biodieselconsists mainly of co-crystallized saturated fatty acid methyl esters(FAME). These problems are well-recognized and various additives havebeen proposed.

Certain additives, called middle distillate cold flow improvers (MDFI)or biodiesel flow improvers (BDFI), reduce the size and change theshape, from plate-like to needle-like structures, of the wax crystalsthat do form. Smaller size crystals are desirable since they are lesslikely to clog the filter whereas needle-like structure are being morelikely to pass through a filter, or form a porous layer of crystals onthe filter. Other additives may also have the effect of retaining thewax crystals in suspension in the fuel, reducing settling and thus alsoassisting in the prevention of blockages. These types of additives areoften termed “wax anti-settling agents” (WASA).

Many WASA have been described over the past years for avoiding thesedimentation of wax crystals inside a fuel.

For example, U.S. Pat. No. 4,400,2708 discloses the efficiency of singlemolecules based on dialkyl amine derivatives of phthalic acid (PAderivatives). In particular are mentioned N,N-dioctadecyl phthalamicacid, N,N-diarachidyl phthalamic acid and phthalic acid bis-dioctadecylamide.

Another example, EP Patent No. 1 935 968 describes suitable waxanti-settling agents to be oil-soluble polar nitrogen of whichsubstituents may be in the form of cations. The WASA are condensates ofcarboxylic acids or their anhydrides with primary or secondary aminescontaining at least one straight chain C₈₋₄₀ alkyl segment. Inparticular, the preferred compound is the amide-amine salt formed byreacting 1 molar portion of phthalic anhydride with 2 molar portions ofdi-(hydrogenated tallow) amine.

In WO International Publication No. 2007/147753 (BASF) a blend of 2 to 3components is used to stabilize wax crystals in fuels and mixes thereofwith biofuels (from B0.1 to B75). The blend consists of 5% to 95% byweight of polar molecule (which is not one of following), 1 to 50% byweight of an amid molecule made from the condensation of a polyaminestructure (having 2 to 1000 N-atoms) and with C₈₋₃₀ fatty acids, andwhich may be mixed with 0 to 50% by weight of a condensate ofα,β-dicarboxylic acid (having 4 to 300 C-atoms) and primary amine. Asexample is given a condensate of ethylenediaminotetraacetic acid (EDTA)with ditallow amine (50 mol %) blended with a condensate of diethylenetriamine and oleic acid (37.5 mol %) and a condensate of maleic acidanhydride with tridecylamine (12.5 mol %).

EP Patent No. 1 451 271 describes the use of oil soluble nitrogencompounds obtained by reaction of aliphatic or aromatic amines withaliphatic or aromatic mono, di-, tri-, or tetracarboxylic acids or theiranhydrides. In particular, two different types of WASA chemistries arecited as part of the WAFI formulation (wax antisettling and flowimprover). One of the chemistry is based on alkenyl-spirolactone reactedwith secondary fatty amines having 8 to 36 carbon atoms. Example isgiven by dodecenyl-spirobislactone condensed with primary and secondarytallow amines. The second chemistry is provided by a terpolymer of vinylmonomers statistically copolymerized with allyl polyglycol ether andmaleic acid anhydride and condensated with primary amines and/oraliphatic alcohol. To illustrate the patent, a terpolymer ofC₁₄/C₁₆-αolefin, maleic anhydride and allylpolyglycol reacted with 2moles of ditallow amines is mentioned as useful wax stabilizer.

As most of the commercial WASA are based on blends of single modifiedmolecules (like NTA, EDTA and PSA) or on modified poly-α-olefins, wepropose as new WASA, a PAMA-based polymeric material having aminofunctionalities (e.g. for monomers dimethylaminoethylmethacrylate(DMAEMA) or dimethylpropylmethacrylamide (DMAPMAm)). These compoundshave good handling properties compared to state of the art componentsand are moreover useful to stabilize wax in fuels or blends thereof.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is providedthe use of a polyalkyl(meth)acrylate comprising monomer units of:

-   (a) 0% to 40% by weight of one or more ethylenically unsaturated    ester compounds of formula (I)

-   -   wherein    -   R is H or CH₃,    -   R¹ represents a linear or branched, saturated or unsaturated        alkyl group with 1 to 9 carbon atoms or a cycloalkyl group with        3 to 9 carbon atoms,    -   R² and R³ independently represent H or a group of the formula        —COOR′, wherein R′ is H or a linear or branched, saturated or        unsaturated alkyl group with 1 to 9 carbon atoms or a cycloalkyl        group with 3 to 9 carbon atoms,

-   (b) 20% to 98% by weight of one or more ethylenically unsaturated    ester compounds of formula (II)

-   -   wherein    -   R is H or CH₃,    -   R⁴ represents a linear or branched, saturated or unsaturated        alkyl group with 10 to 22 carbon atoms,    -   R⁵ and R⁶ independently represent H or a group of the formula        —COOR″, wherein R″ is H or a linear or branched, saturated or        unsaturated alkyl group with 10 to 22 carbon atoms,

-   (c) 0% to 10% by weight of one or more ethylenically unsaturated    ester compounds of formula (III)

-   -   wherein    -   R is H or CH₃,    -   R⁷ represents a linear or branched, saturated or unsaturated        alkyl group with 23 to 40 carbon atoms,    -   R⁸ and R⁹ independently represent H or a group of the formula        —COOR′″ wherein R′″ is H or a linear or branched, saturated or        unsaturated alkyl group with 23 to 40 carbon atoms,

-   (d) 0% to 30% by weight of vinyl aromatic monomers, and

-   (e) 2% to 80% by weight of at least one N-dispersant monomer,    wherein components (a) to (e) add up to 100% by weight, for    improving the cold flow properties of fuel oil compositions.

DETAILED DESCRIPTION OF THE INVENTION

Within the context of the present invention, the term “alkyl(meth)acrylate” refers to both the alkyl acrylate and the alkylmethacrylate species or a mixture thereof. Alkyl methacrylates arepreferred.

Non-limiting examples of component (a) include (meth)acrylates,fumarates and maleates which derive from saturated alcohols such asmethyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate,isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl(meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylateand nonyl (meth)acrylate; cycloalkyl (meth)acrylates, like cyclopentyl(meth)acrylate, cyclohexyl (meth)acrylate and 3-vinylcyclohexyl(meth)acrylate; (meth)acrylates that derive from unsaturated alcoholslike 2-propynyl (meth)acrylate, allyl (meth)acrylate and vinyl(meth)acrylate; and the corresponding fumarates and maleates.

Monomer (a) is present in an amount of 0% to 40% by weight, preferably0% to 20% by weight based on the total weight of components (a), (b),(c), (d) and (e).

In one embodiment, the amount of monomer (a) is at least 0.1% by weight,preferably at least 0.5% by weight.

In a preferred embodiment the amount of monomer (a) is 0%.

Non-limiting examples of component (b) include (meth)acrylates,fumarates and maleates that derive from saturated alcohols, such as2-tert-butylheptyl (meth)acrylate, 3-isopropylheptyl (meth)acrylate,2-n-propylheptyl (meth)acrylate, decyl (meth)acrylate, undecyl(meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate,2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate,5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl(meth)acrylate, hexadecyl (meth)acrylate, 2-methylhexadecyl(meth)acrylate, heptadecyl (meth)acrylate, 5-isopropylheptadecyl(meth)acrylate, 4-tert-butyloctadecyl (meth)acrylate, 5-ethyloctadecyl(meth)acrylate, 3-isopropyloctadecyl (meth)acrylate, octadecyl(meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate ordocosyl (meth)acrylate; (meth)acrylates that derive from unsaturatedalcohols, such as oleyl (meth)acrylate; cycloalkyl (meth)acrylates suchas bornyl (meth)acrylate, 2,4,5-tri-tert-butyl-3-vinylcyclohexyl(meth)acrylate, 2,3,4,5-tetra-tert-butylcyclohexyl (meth)acrylate;oxiranyl methacrylates such as 10,11-epoxyhexadecyl methacrylate; andthe corresponding fumarates and maleates.

Monomer (b) is present in an amount of 20% to 98% by weight, preferably50% to 95% by weight, more preferably 70% to 90% by weight based on thetotal weight of components (a), (b), (c), (d) and (e).

In a preferred embodiment monomer (b) is a C₈₋₁₅-alkyl (meth)acrylate,preferably commercial lauryl(meth)acrylate, or a C₁₀₋₁₅-alkyl(meth)acrylate fraction. More preferably the backbone monomer is aC₈₋₁₅-alkyl methacrylate, preferably commercial lauryl methacrylate or aC₁₀₋₁₅-alkyl methacrylate fraction.

Non-limiting examples of component (c) include (meth)acrylates thatderive from saturated alcohols, such as cetyleicosyl (meth)acrylate,stearyleicosyl (meth)acrylate and/or eicosyltetratriacontyl(meth)acrylate; as well as the corresponding fumarates and maleates.

In accordance with the invention, aromatic groups denote radicals ofmonocyclic or polycyclic aromatic compounds having preferably 6 to 20,more particularly 6 to 12, C atoms, such as, for example, phenyl,naphthyl or biphenylyl, preferably phenyl.

Heteroaromatic groups identify aryl radicals in which at least one CHgroup is replaced by N and/or at least two adjacent CH groups arereplaced by S, NH or O. These radicals include, among others, groupsderived from thiophene, furan, pyrrole, thiazole, oxazole, imidazole,isothiazole, isoxazole, pyrazole, 1,3,4-oxadiazole, 1,3,4-thiadiazole,1,3,4-triazole, 1,2,4-oxa-diazole, 1,2,4-thiadiazole, 1,2,4-triazole,1,2,3-triazole, 1,2,3,4-tetrazole, benzo[b]thiophene, benzo[b]furan,indole, benzo[c]thiophene, benzo[c]furan, isoindole, benzoxazole,benzothiazole, benzimidazole, benzisoxazole, benzisothiazole,benzopyrazole, benzothiadiazole, benzotriazole, dibenzofuran,dibenzothiophene, carbazole, pyridine, pyrazine, pyrimidine, pyridazine,1,3,5-triazine, 1,2,4-triazine, 1,2,4,5-triazine, quinoline,isoquinoline, quinoxaline, quinazoline, cinnoline, 1,8-naphthyridine,1,5-naphthyridine, 1,6-naphthyridine, 1,1′-naphthyridine, phthalazine,pyridopyrimidine, purine, pteridine or 4H-quinolizine.

The preferred alkyl groups include the methyl, ethyl, propyl, isopropyl,1-butyl, 2-butyl, 2-methylpropyl, tert-butyl, pentyl, 2-methylbutyl,1,1-dimethylpropyl, hexyl, heptyl, octyl, 1,1,3,3-tetramethylbutyl,nonyl, 1-decyl, 2-decyl, undecyl, dodecyl, pentadecyl and the eicosylgroup.

The preferred cycloalkyl groups include the cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl and the cyclooctyl group, which areunsubstituted or substituted by branched or non-branched alkyl groups.

The preferred alkenyl groups include the vinyl, allyl,2-methyl-2-propene, 2-butenyl, 2-pentenyl, 2-decenyl and the 2-eicosenylgroup.

Monomer (c) is present in an amount of 0% to 10% by weight based on thetotal weight of components (a), (b), (c), (d) and (e).

In one embodiment, the amount of monomer (c) is at least 0.1% by weight,preferably at least 0.5% by weight.

Monomer (d), when present may be a vinyl aromatic monomer such asstyrene and substituted styrenes although other vinyl monomers can alsobe used. The substituted styrenes include styrenes which are substitutedwith one or more substituents selected from the group consisting ofhalogen, amino, alkoxy with 1 to 12 carbon atoms in the alkyl residue,carboxy, hydroxy, sulfonyl, hydrocarbyl with 1 to 12 carbon atoms andother substituents. Exemplary of the hydrocarbyl-substituted styrenesare alpha-methylstyrene, para-tert-butylstyrene, alpha-ethylstyrene, andpara-lower alkoxy styrene having 1 to 12 carbon atoms. Mixtures of twoor more vinyl monomers can be used. Styrene is preferred.

The amount of vinyl monomer used is from 0% to 30% by weight, and whenpresent, preferably from 5% to 25% by weight, more preferably 10% to 20%by weight, based on the total weight of components (a), (b), (c), (d)and (e).

Monomer (e) is at least one monomer selected from the group consistingof N-vinylic monomers, (meth)acrylic esters, (meth)acrylic amides and(meth)acrylic imides each with dispersing moieties in the side chain andmay be an N-dispersant monomer of the formula (IV)

whereinR¹⁰, R¹¹ and R¹² independently are H or a linear or branched, saturatedor unsaturated alkyl group with 1 to 5 carbon atoms andR¹³ is either a group selected from —C(O)—O—R¹⁴, —C(O)—NH—R¹⁴,—C(NR¹⁵)—O—R¹⁴, —C(NR¹⁵)—NH—R¹⁴ and—C(O)—[NH—C₂₋₁₀-alkylene]_(x)-NR¹⁶R¹⁷, whereinR¹⁵ represents a linear or branched, saturated or unsaturated alkylgroup with 1 to 5 carbon atoms or an aryl group andR¹⁴ represents a linear or branched alkyl group with 1 to 20 carbonatoms which is unsubstituted or substituted by a group —NR¹⁶R¹⁷, whereinR¹⁶ and R¹⁷ independently represent H or a linear or branched alkylgroup with 1 to 8 carbon atoms, or wherein R¹⁶ and R¹⁷ are part of a 4-to 8-membered saturated or unsaturated ring containing optionally one ormore hetero atoms chosen from the group consisting of nitrogen, oxygenor sulphur, wherein said ring may be further substituted with alkyl oraryl groups, and x represents a number 1, 2, 3 or 4, orR¹³ is a group —NR¹⁸R¹⁹, wherein R¹⁸ and R¹⁹ are part of a 4- to8-membered saturated or unsaturated ring, containing at least one carbonatom as part of the ring which forms a double bond to a hetero atomchosen from the group consisting of nitrogen, oxygen or sulphur, whereinsaid ring may be further substituted with alkyl or aryl groups.

In one embodiment, R¹⁴ represents H or a linear or branched alkyl groupwith 2 to 6 carbon atoms.

Non-limiting examples of N-dispersant monomers include those selectedfrom the group consisting of vinyl substituted nitrogen heterocyclicmonomers, for example vinyl pyridine and N-vinyl-substituted nitrogenheterocyclic monomers, for example, N-vinyl imidazole, N-vinylpyrrolidinone (NVP), morpholinoethyl methacrylate and N-vinylcaprolactam, dialkylaminoalkyl acrylate and methacrylate monomers, forexample N,N-dialkylaminoalkyl (meth)acrylates, for exampleN,N-dimethylaminoethyl methacrylate (DMAEMA), tert-butyl aminoethylmethacrylate, dialkylaminoalkyl acrylamide and methacrylamide monomers,for example di-lower alkylaminoalkylacrylamide, especially where eachalkyl or aminoalkyl group contains from 1 to 8 carbon atoms, especiallyfrom 1 to 3 carbon atoms, for example N,N-di lower alkyl, especially,N,N-dimethylaminopropylmethacrylamide (DMAPMAm),dimethylaminopropylacrylamide, dimethylaminoethylacrylamide, N-tertiaryalkyl acrylamides and corresponding methacrylamides, for exampletertiary butyl acrylamide, vinyl substituted amines, and N-vinyl lactamsuch as N-vinyl pyrrolidone (NVP).

By virtue to the presence of basic nitrogen groups in the polymer, it isreadily apparent that some or all of the nitrogen atoms may be convertedto a salt form by reaction with an acid. Accordingly, the polymer may bepartially or completely neutralized by reaction with acidic compoundsand still be within the scope of the invention.

In another embodiment, the N-dispersant monomer may comprise acombination of (i) acrylamide based N-dispersant monomer of the formula(IV)

-   -   wherein    -   R¹⁰, R¹¹ and R¹² are independently H or a linear or branched,        saturated or unsaturated alkyl group with 1 to 5 carbon atoms        and    -   R¹³ is a group selected from —C(O)—O—R¹⁴, —C(O)—NH—R¹⁴,        —C(NR¹⁵)—O—R¹⁴, —C(NR¹⁵)—NH—R¹⁴ and        —C(O)—[NH—C₂₋₁₀-alkylene]_(x)-NR¹⁶R¹⁷, wherein    -   R¹⁵ is an alkyl or aryl group and R¹⁴ represents a linear or        branched alkyl group with 1 to 20 carbon atoms which is        unsubstituted or substituted by a group —NR¹⁶R¹⁷ wherein R¹⁶ and        R¹⁷ independently represent H or a linear or branched alkyl        group with 1 to 8 carbon atoms, or wherein R¹⁶ and R¹⁷ are part        of a 4 to 8 membered saturated or unsaturated ring containing        optionally one or more hetero atoms chosen from the group        consisting of nitrogen, oxygen or sulphur, wherein said ring may        be further substituted with alkyl or aryl groups, and x        represents a number 1, 2, 3 or 4,    -   and        (ii) an N-dispersant monomer of the formula (IV)

-   -   wherein    -   R¹⁰, R¹¹ and R¹² independently are H or an alkyl group with 1 to        5 carbon atoms and R¹³ is a group —NR¹⁸R¹⁹, wherein R¹⁸ and R¹⁹        are part of a 4- to 8-membered saturated or unsaturated ring,        containing at least one carbon atom as part of the ring which        forms a double bond to a hetero atom chosen from the group        consisting of nitrogen, oxygen or sulphur, wherein said ring may        be further substituted with alkyl or aryl groups.

The N-dispersant monomer may specifically be at least one monomerselected from the group consisting of N-vinyl pyrrolidinone,N,N-dimethylaminoethyl methacrylate andN,N-dimethylaminopropylmethacrylamide or a mixture thereof.

The amount of N-dispersant monomer is typically from 2% to 80%,preferably from 5% to 50% by weight, and even more preferably from 10%to 30% by weight, based on the total weight of components (a), (b), (c),(d) and (e).

It may be beneficial to use at least two N-dispersant monomers,especially when the total amount of N-dispersant monomer is at the lowend of the recited range.

The polyalkyl(meth)acrylate typically have a number average molecularweight M_(n) of from 1000 to 1000000 g/mol, preferably 2000 to 100000g/mol, more preferably 2500 to 100000 g/mol, even more preferably 2500to 50000 g/mol and especially preferred 4000 to 20000 g/mol as measuredby size exclusion chromatography, calibrated versus a polystyrenestandard.

The polydispersity M_(w)/M_(n) of the polyalkyl(meth)acrylate polymerspreferably is in the range of from 1 to 8, especially from 1.05 to 6.0,more preferably from 1.1 to 5.0 and most preferably from 1.3 to 2.5. Theweight average molecular weight M_(w), the number average molecularweight M_(n) and the polydispersity M_(w)/M_(n) can be determined by GPCusing a methyl methacrylate polymer as standard.

As a preferred first aspect of the invention, there is provided the useof a polyalkyl(meth)acrylate comprising monomer units of:

-   (a) 20% to 98% by weight of one or more ethylenically unsaturated    ester compounds of formula (II)

-   -   wherein    -   R is H or CH₃,    -   R⁴ represents a linear or branched, saturated or unsaturated        alkyl group with 10 to 22 carbon atoms,    -   R⁵ and R⁶ independently represent H or a group of the formula        —COOR″, wherein R″ is H or a linear or branched, saturated or        unsaturated alkyl group with 10 to 22 carbon atoms,

-   (b) 0% to 10% by weight of one or more ethylenically unsaturated    ester compounds of formula (III)

-   -   wherein    -   R is H or CH₃,    -   R⁷ represents a linear or branched, saturated or unsaturated        alkyl group with 23 to 40 carbon atoms,    -   R⁸ and R⁹ independently represent H or a group of the formula        —COOR′″ wherein R′″ is H or a linear or branched, saturated or        unsaturated alkyl group with 23 to 40 carbon atoms,

-   (c) 0% to 30% by weight of vinyl aromatic monomers, and

-   (d) 2% to 80% by weight of at least one N-dispersant monomer,    wherein components (a) to (e) add up to 100% by weight, for    improving the cold flow properties of fuel oil compositions.

The architecture of the polyalkyl(meth)acrylate polymers is not criticalfor many applications and properties. Accordingly, these polymers may berandom copolymers, gradient copolymers, block copolymers and/or graftcopolymers. Block copolymers and gradient copolymers can be obtained,for example, by altering the monomer composition discontinuously duringthe chain growth. According to the present invention, the polymers arepreferably random copolymers.

The combination according to the present invention is suitable as anadditive to fuels, especially middle distillate fuels. Middle distillatefuels are often referred to as fuels oils. They find use in particularin gas oils, petroleum, diesel oils or diesel fuels or light and extralight heating oils and have generally boiling points from 150° C. to400° C.

The combination according to the present invention can be added to thefuels directly and undiluted or as concentrate (solution) in a suitablesolvent, typically a hydrocarbon solvent.

A further embodiment of the present invention comprises the use of aconcentrate, comprising:

-   (A) 30% to 90% by weight of a polyalkyl(meth)acrylate comprising    monomer units of:-   (a) 0% to 40% by weight of one or more ethylenically unsaturated    ester compounds of formula (I)

-   -   wherein    -   R is H or CH₃,    -   R¹ represents a linear or branched, saturated or unsaturated        alkyl group with 1 to 9 carbon atoms or a cycloalkyl group with        3 to 9 carbon atoms,    -   R² and R³ independently represent H or a group of the formula        —COOR′, wherein R′ is H or a linear or branched, saturated or        unsaturated alkyl group with 1 to 9 carbon atoms or a cycloalkyl        group with 3 to 9 carbon atoms,

-   (b) 20% to 98% by weight of one or more ethylenically unsaturated    ester compounds of formula (II)

-   -   wherein    -   R is H or CH₃,    -   R⁴ represents a linear or branched, saturated or unsaturated        alkyl group with 10 to 22 carbon atoms,    -   R⁵ and R⁶ independently represent H or a group of the formula        —COOR″, wherein R″ is H or a linear or branched, saturated or        unsaturated alkyl group with 10 to 22 carbon atoms,

-   (c) 0% to 10% by weight of one or more ethylenically unsaturated    ester compounds of formula (III)

-   -   wherein    -   R is H or CH₃,    -   R⁷ represents a linear or branched, saturated or unsaturated        alkyl group with 23 to 40 carbon atoms,    -   R⁸ and R⁹ independently represent H or a group of the formula        —COOR′″ wherein R′″ is H or a linear or branched, saturated or        unsaturated alkyl group with 23 to 40 carbon atoms,

-   (d) 0% to 30% by weight vinyl aromatic monomers, and

-   (e) 2% to 80% by weight of at least one N-dispersant monomer,    wherein components (a) to (e) add up to 100 weight %; and

-   (B) 10% to 70% by weight of a hydrocarbon solvent/an oil    as an additive to fuels, especially middle distillate fuels, for    improving the cold flow properties of fuel oil compositions.

Common hydrocarbon solvents in this context are aliphatic or aromatichydrocarbons such as xylenes or mixtures of high-boiling aromatics asfor example Solvent Naphtha. Middle distillate fuels themselves may alsobe used as the solvent for such concentrates.

The concentrate may comprise from 10% to 70% by weight, preferably from30% to 65% by weight, and more preferred from 45% to 60% by weight,based on the total amount of the concentrate, of the inventivepolyalkyl(meth(acrylate) as described above.

In a preferred embodiment, the inventive concentrate is used as anadditive to fuels which consists of

-   (i) 0% to 99% by weight, preferably 0.5% to 75% by weight, of at    least one biofuel oil which is based on fatty acid esters and-   (ii) 1% to 100% by weight, preferably 25% to 99.5% by weight, of    middle distillates of fossil origin and/or of vegetable and/or    animal origin, which are essentially hydrocarbon mixtures and are    free of fatty acid esters.

The fuel component (i) shall be understood to mean middle distillatefuels boiling in the range of from 120° C. to 450° C. Such middledistillate fuels are used in particular as diesel fuel, heating oil orkerosene. Preference is given to diesel fuel and heating oil.

The fuel composition of the present invention may comprise diesel fuelof mineral origin, i.e. diesel, gas oil or diesel oil. Mineral dieselfuel is widely known per se and is commercially available. This isunderstood to mean a mixture of different hydrocarbons which is suitableas a fuel for a diesel engine. Diesel can be obtained as a middledistillate, in particular by distillation of crude oil. The mainconstituents of the diesel fuel preferably include alkanes, cycloalkanesand aromatic hydrocarbons having about 10 to 22 carbon atoms permolecule.

Preferred diesel fuels of mineral origin boil in the range of 120° C. to450° C., more preferably 170° C. and 390° C. Preference is given tousing those middle distillates which contain 0.2% by weight of sulphurand less, preferably less than 0.05% by weight of sulphur, morepreferably less than 350 ppm of sulphur, in particular less than 200 ppmof sulphur and in special cases less than 50 ppm of sulphur, for exampleless than 10 ppm of sulphur. They are preferably those middledistillates which have been subjected to refining under hydrogenatingconditions, and which therefore contain only small proportions ofpolyaromatic and polar compounds. They are preferably those middledistillates which have 95% distillation points below 370° C., inparticular below 350° C. and in special cases below 330° C. Syntheticfuels, as obtainable, for example, by the Fischer-Tropsch process or gasto liquid processes (GTL), are also suitable as diesel fuels of mineralorigin.

The kinematic viscosity of diesel fuels of mineral origin to be usedwith preference is in the range of 0.5 to 8 mm²/s, more preferably 1 to5 mm²/s, and especially preferably 2 to 4.5 mm²/s or 1.5 to 3 mm²/s,measured at 40° C. to ASTM D 445.

The fuel compositions of the present invention may comprise at least 20%by weight, in particular at least 30% by weight, preferably at least 50%by weight, more preferably at least 70% by weight and most preferably atleast 80% by weight of diesel fuels of mineral origin.

Furthermore, the present fuel composition may comprise at least onebiodiesel fuel component. Biodiesel fuel is a substance, especially anoil, which is obtained from vegetable or animal material or both, or aderivative thereof which can be used in principle as a replacement formineral diesel fuel.

In a preferred embodiment, the biodiesel fuel, which is frequently alsoreferred to as “biodiesel” or “biofuel” comprises fatty acid alkylesters formed from fatty acids having preferably 6 to 30, morepreferably 12 to 24 carbon atoms, and monohydric alcohols having 1 to 4carbon atoms. In many cases, some of the fatty acids may contain one,two or three double bonds. The monohydric alcohols include in particularmethanol, ethanol, propanol and butanol, methanol being preferred.

Examples of oils which derive from animal or vegetable material andwhich can be used in accordance with the invention are palm oil,rapeseed oil, coriander oil, soya oil, cottonseed oil, sunflower oil,castor oil, olive oil, groundnut oil, corn oil, almond oil, palm kerneloil, coconut oil, mustard seed oil, oils which are derived from animaltallow, especially beef tallow, bone oil, fish oils and used cookingoils. Further examples include oils which derive from cereal, wheat,jute, sesame, rice husks, jatropha, algae, arachis oil and linseed oil.The fatty acid alkyl esters to be used with preference may be obtainedfrom these oils by processes known in the prior art.

Preference is given in accordance with the invention to highlyC16:0/C18:0-glyceride-containing oils, such as palm oils and oils whichare derived from animal tallow, and also derivatives thereof, especiallythe palm oil alkyl esters which are derived from monohydric alcohols.Palm oil (also: palm fat) is obtained from the fruit flesh of the palmfruits. The fruits are sterilized and pressed. Owing to their highcarotene content, fruits and oils have an orange-red colour which isremoved in the refining. The oil may contain up to 80% C18:0-glyceride.

Particularly suitable biodiesel fuels are lower alkyl esters of fattyacids. Useful examples here are commercial mixtures of the ethyl,propyl, butyl and especially methyl esters of fatty acids having 6 to30, preferably 12 to 24, more preferably 14 to 22 carbon atoms, forexample of caprylic acid, capric acid, lauric acid, myristic acid,palmitic acid, margaric acid, stearic acid, arachic acid, behenic acid,lignoceric acid, cerotic acid, palmitoleic acid, stearic acid, oleicacid, elaidic acid, petroselic acid, ricinoleic acid, elaeostearic acid,linoleic acid, linolenic acid, eicosanoic acid, gadoleic acid,docosanoic acid or erucic acid.

In a particular aspect of the present invention, a biodiesel fuel isused which comprises preferably at least 10% by weight, more preferablyat least 30% by weight and most preferably at least 40% by weight ofsaturated fatty acid esters which are derived from methanol and/orethanol. Especially, these esters have at least 16 carbon atoms in thefatty acid part. These include in particular the esters of palmitic acidand stearic acid.

The inventive fuel composition may comprise further additives in orderto achieve specific solutions to problems. These additives include othercold flow improvers different than those described above, dispersants,for example wax dispersants and dispersants for polar substances,conductivity improvers, demulsifiers, defoamers, lubricity additives,additional antioxidants, cetane number improvers, detergents, dyes,corrosion inhibitors, metal deactivators, metal passivators and/orodourants.

A further object of the present invention is directed to a method forimproving the cold flow properties of fuel oil compositions, comprisingthe steps of adding at least one polyalkyl(meth)acrylate as describedabove to fuels, especially to middle distillate fuels and blendsthereof, and mixing the resulting composition. The addition ispreferably done at temperatures above the cloud point of the used fuels.

A further object of the present invention is directed to a method forimproving the cold flow properties of fuel oil compositions, comprisingthe steps of:

adding a concentrate comprising

-   -   (i) at least one polyalkyl(meth)acrylate as described above and    -   (ii) a hydrocarbon solvent/an oil        to fuels, especially to middle distillate fuels and blends        thereof; and        (finally) reducing the tendency of sedimentation of paraffin        waxes and sludgy material in the fuels at low temperatures.

Process for Preparing PAMAs

The monomer mixtures described above can be polymerized by methods knownin the art. The copolymers of this invention may be prepared byprocesses comprising reacting monomers (a) to (e) in the presence of afree radical initiator and optionally in the presence of a chaintransfer agent. The monomers may be reacted concurrently.

Conventional radical initiators can be used to perform a classic radicalpolymerization. These initiators are well known in the art. Examples forthese radical initiators are azo initiators like2,2′-azodiisobutyronitrile (AIBN), 2,2′-azobis(2-methylbutyronitrile)and 1,1-azobiscyclohexane carbonitrile; peroxide compounds, e.g. methylethyl ketone peroxide, acetyl acetone peroxide, dilauryl peroxide,tert-butyl per-2-ethyl hexanoate, ketone peroxide, methyl isobutylketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tert-butylperbenzoate, tert-butyl peroxy isopropyl carbonate,2,5-bis(2-ethylhexanoyl-peroxy)-2,5-dimethyl hexane, tert-butyl peroxy2-ethyl hexanoate, tert-butyl peroxy-3,5,5-trimethyl hexanoate, dicumeneperoxide, 1,1-bis(tert-butyl peroxy) cyclohexane, 1,1-bis(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, di-tert-butyl peroxide, cumenehydroperoxide and tert-butyl hydroperoxide.

Low molecular weight poly(meth)acrylates can be obtained by using chaintransfer agents. This technology is ubiquitously known and practiced inthe polymer industry and is described in Odian, Principles ofPolymerization, 1991. Examples of chain transfer agents are aldehydes orsulphur containing compounds such as thiols, e.g. n- andtert-dodecanethiol, 2-mercaptoethanol, and mercapto carboxylic acidesters, e.g. methyl-3-mercaptopropionate. Preferred chain transferagents contain up to 20, especially up to 15 and more preferably up to12 carbon atoms. Furthermore, chain transfer agents may contain at least1, especially at least 2 oxygen atoms.

Furthermore, novel polymerization techniques such as ATRP (Atom TransferRadical Polymerization) and or RAFT (Reversible Addition FragmentationChain Transfer) can be applied to obtain useful poly(meth)acrylates.These methods are well known. The ATRP reaction method is described, forexample, by J.-S. Wang, et al., J. Am. Chem. Soc., Vol. 117, pp.5614-5615 (1995), and by Matyjaszewski, Macromolecules, Vol. 28, pp.7901-7910 (1995). Moreover, the patent applications WO 96/30421, WO97/47661, WO 97/18247, WO 98/40415 and WO 99/10387 disclose variationsof the ATRP explained above to which reference is expressly made forpurposes of the disclosure. The RAFT method is extensively presented inWO 98/01478, for example, to which reference is expressly made forpurposes of the disclosure.

The polymerization can be carried out at normal pressure, reducedpressure or elevated pressure. The polymerization temperature is alsonot critical. However, in general it lies in the range of −20° C. to200° C., preferably 0° C. to 130° C. and especially preferably 60° C. to120° C., without any limitation intended by this.

The polymerization can be carried out with or without solvents. The termsolvent is to be broadly understood here.

Preferably, the polymerization is carried out in a nonpolar solvent.Among these solvents are hydrocarbon solvents, such as aromatic solventslike toluene, benzene and xylene, saturated hydrocarbons such ascyclohexane, heptane, octane, nonane, decane, dodecane, which can alsooccur in branched form. These solvents can be used individually and as amixture. Especially preferred solvents are mineral oils and syntheticoils and mixtures of these. Of these, mineral oils are most preferred.

Mineral oils are substantially known and commercially available. Theyare generally obtained from petroleum or crude oil by distillationand/or refining and optionally additional purification and processingmethods, especially the higher-boiling fractions of crude oil orpetroleum fall under the concept of mineral oil. In general, the boilingpoint of the mineral oil is higher than 200° C., preferably higher than300° C., at 50 mbar. Preparation by low temperature distillation ofshale oil, coking of hard coal, distillation of lignite under exclusionof air as well as hydrogenation of hard coal or lignite is likewisepossible. To a small extent, mineral oils are also produced from rawmaterials of plant origin (for example jojoba, rapeseed oil) or animalorigin (for example neatsfoot oil). Accordingly, mineral oils exhibitdifferent amounts of aromatic, cyclic, branched and linear hydrocarbonsin each case, according to origin.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil); liquid petroleum oils and hydro-refined, solvent-treated oracid-treated mineral oils of the paraffinic, naphthenic and mixedparaffinic-naphthenic types.

These solvents can be used, among other ways, in an amount of 1% to 99%by weight, preferably 5% to 95% weight, especially preferably 5% to 60%by weight and most preferably 10% to 50% by weight, with respect to thetotal weight of the mixture, without any limitation intended to beimplied by this.

In one embodiment, the process comprises reacting a mixture of themonomers, often by first heating a portion, often from about 20% toabout 60%, of the mixture until reaction is evident, usually by notingan exotherm, then adding and reacting the balance of the mixture ofmonomers, either portion wise, or all at once.

Experimental Part

Sedimentation tests were carried out with state of the art WASA, basedon either ethylenediaminotetraacetic acid (EDTA), phthalic anhydride(PA) or Alpha-olefin and with the products of the invention. The list oftested WASA components is given below. For all polymers used in thisstudy, the number average molecular weight M_(n) of the polymer isaround 5000 g/mol and the mass average molecular weight M_(w) of thepolymer is around 9000 g/mol. If there is any exception in the molecularweight, then WASA are noted with ⁽*⁾.

-   Component A: EDTA condensed with 4 moles of di-tallow amine in    solvent Naphta;    -   product content=70%-   Component B: Phthalic acid anhydride condensed with 2 moles of    di-tallow amine in solvent Naphta;    -   product content=70%-   Component C: Alpha-olefin-stat-MA condensed with di-tallow amine in    solvent Naphta; polymer content=70%-   Component D: dodecyl/pentadecyl methacrylate    -   polymer content=70% in ShelIsol A 150 ND-   Component E: dodecyl/pentadecyl    methacrylate-stat-2-dimethylaminoethylmethacrylate (70/30 wt %);    -   polymer content=70% in ShelIsol A 150 ND-   Component F: dodecyl/pentadecyl    methacrylate-stat-2-dimethylaminoethylmethacrylate (85/15 wt %);    -   polymer content=70% in ShelIsol A 150 ND-   Component G: lauryl methacrylate/stearyl    methacrylate-stat-dimethylaminoethylmethacrylate (70/30 wt %);    -   polymer content=70% in ShelIsol A 150 ND-   Component H: dodecyl/pentadecyl    methacrylate-stat-dimethylaminopropylmethacrylamide (70/30 wt %);    -   polymer content=70% in ShelIsol A 150 ND

Table 1 below gives an overview of the different WASA combinationstested.

TABLE 1 compositions tested as WASA. Values given in wt %. W1 W2 W3 W4W5 W6 W7 W8 Component A 100 Component B 100 Component C 100 Component D100 Component E 100 Component F 100 Component G 100 Component H 100

W1 to W4 represent comparative examples and W5 to W8 represent examplesof the invention.

Components Preparation Component A:

12.5 g EDTA, 77.5 g ditallow amine and 0.014 g p-toluene sulfonic acidwere molten at temperature of 150° C. The reaction was allowed to takeplace during 30 minutes, and after cooling down, was diluted in solventNaphta to 70 wt %.

Component B:

35.0 g PSA, 213.2 g ditallow amine and 62.1 g solvent naphtha weremolten at temperature of 150° C. The reaction was allowed to take placeduring 180 minutes, and after cooling down, was further diluted insolvent Naphta to 70 wt %.

Component C:

88.1 g solvent naphtha, 10.5 g maleic anhydride and 11.1 gC_(16/18)-alpha olefin were charged in the kettle and heated up to 140°C. A mixture of C_(16/18)-alpha olefin (188.4 g) and a 50% concentratedsolution of 2,2-bis-(tert-butylperoxy)butane (3.8 g) was continuouslyadded over 3.5 h. After 1.5 h, the temperature was reduced to 100° C.,where 0.42 g tert.-butylper-2-ethylhexanoat was added. The batch wasstirred over night at 100° C. All steps were done in an inert gasatmosphere. Then, 150 g of the C_(16/18)-alpha olefin-maleic anhydridecopolymer was added to 59.6 g ditallow amine and 25.5 g solvent naphtha.The solution was heated up to 140° C. and stirred over night. Theforming water was removed directly with a permanent inert gas flow.

Component D:

107.5 g solvent naphtha was charged in the kettle and heated up to 140°C. A mixture of dodecyl/pentadecyl methacrylate (262.5 g) and a 50%concentrated solution of 2,2-bis-(tert-butylperoxy)butan (10.0 g) werecontinuously added over 5 h. After 1.5 h, the temperature was reduced to100° C., and 0.5 g tert-butylper-2-ethylhexanoat was added. The batchwas stirred over night at 100° C. All steps were done in an inert gasatmosphere.

Component E:

143.4 g solvent naphtha was charged in the kettle and heated up to 140°C. A mixture of dodecyl/pentadecyl methacrylate (245.0 g),2-dimethylaminoethylmethacrylate (105.0 g) and a 50% concentratedsolution of 2,2-bis-(tert-butylperoxy)butan (13.3 g) was continuouslyadded over 5 h. After 1.5 h, the temperature was reduced to 100° C., and0.7 g tert-butylper-2-ethylhexanoat was added. The batch was stirredover night at 100° C. All steps were done in an inert gas atmosphere.

Component F:

143.4 g solvent naphtha was charged in the kettle and heated up to 140°C. A mixture of dodecyl/pentadecyl methacrylate (297.5 g),2-dimethylaminoethylmethacrylate (52.5 g) and a 50% concentratedsolution of 2,2-bis-(tert-butylperoxy)butan (13.3 g) was continuouslyadded over 5 h. After 1.5 h, the temperature was reduced to 100° C., and0.7 g tert-butylper-2-ethylhexanoat was added. The batch was stirredover night at 100° C. All steps were done in an inert gas atmosphere.

Component G:

143.4 g solvent naphtha was charged in the kettle and heated up to 140°C. A mixture of lauryl methacrylate/stearylmethacrylate (245.0 g),2-dimethylaminoethylmethacrylate (105.0 g) and a 50% concentratedsolution of 2,2-bis-(tert-butylperoxy)butan (13.3 g) was continuouslyadded over 5 h. After 1.5 h, the temperature was reduced to 100° C., and0.7 g tert-butylper-2-ethylhexanoat was added. The batch was stirredover night at 100° C. All steps were done in an inert gas atmosphere.

Component H:

143.4 g solvent naphtha was charged in the kettle and heated up to 140°C. A mixture of dodecyl/pentadecyl methacrylate (245.0 g),dimethylaminopropylmethacrylamide (105.0 g) and a 50% concentratedsolution of 2,2-bis-(tert-Butylperoxy)butan (13.3 g) were continuouslyadded over 5 h. After 1.5 h, the temperature was reduced to 100° C., and0.7 g tert-butylper-2-ethylhexanoat was added. The batch was stirredover night at 100° C. All steps were done in an inert gas atmosphere.

Handling Properties:

The handling properties, i.e. temperature limits for handling of thedifferent WASA have been compared by determining cloud and pour points(according to ASTM D97 and D2500 respectively). For the tests, WASA aredissolved in Shellsol A 150N D at a concentration of 70% (as mentionedabove in the “components” part).

In the Table 2 below, we can clearly see that W1 to W4 (reference WASA)display much higher CP and PP than the products of the invention W5 andW8 and therefore showing poorer handling properties. Moreover inventionexamples are clear without any turbidity whereas references are hazy orsolid at room temperature.

TABLE 2 Cold flow properties of the WASA 70% in Shellsol A 150 ND. PP CPvisual appearence WASA [° C.] [° C.] after 3 days W1 33.0 35.0 solid atRT W2 6.0 13.0 liquid & strongly hazy W3 30.0 31.0 solid at RT W5 −57.0−53.0 liquid & clear W8 −48.0 −45.0 liquid & clear

Anti-Sedimentation Properties

The sedimentation tests were carried out in B0 and B10 diesel based onthree different fossil diesel fuels (see characteristics displayedbelow).

DK1: CP (ISO 3015)=−3.3° C.; CFPP (EN 116)=−10° C.; Density d15 (DIN51577)=0.8257 g/ml; Distillation begin & end=163° C. & 364° C.;n-Paraffin content=25 wt %.DK2: CP (ISO 3015)=−2.3° C.; CFPP (EN 116)=−5° C.; Density d15 (DIN51577)=0.8284 g/ml; Distillation begin & end=170° C. & 356° C.;n-Paraffin content=18 wt %.DK3: CP (ISO 3015)=−8.1° C.; CFPP (EN 116)=−12° C.; Density d15 (DIN51577)=0.8282 g/ml; Distillation begin & end=245° C. & 340° C.;n-Paraffin content=25 wt %

In a typical sedimentation test, 500 mL glassware containing the fuelblended with the additives to be tested (250 ppm of EVA-based MDFI and150 ppm of WASA) is plunged in an ethanol bath. Before sedimentation,CP, CFPP and PP of the sample are measured. The ethanol bath is cooleddown to a certain temperature depending on the CP and PP of thefuel+additives as the sample should not freeze (temperature well abovePP and below CP). Cooling rate is of 0.24° C./min and the sample is letat temperature 16 hours long. After this period of time, 80% of theupper volume contained in the glassware, the upper phase, is carefullyremoved and with the remaining 20%, the bottom phase, CP was determinedafter homogenization.

ΔCP describes the difference between CP “20% remaining” and CP“initial”. The smaller the ΔCP is the more efficient the waxanti-settling agent is. In general it is expected that a good WASAprovides ΔCP of 2° C. or below.

TABLE 3 ΔCP of B0 and B10 DK1 treated with WASA comparative examples (W1and W3) and invention products (W5-8). WASA with * have M_(n) around24000 g/mol. Fuel type EVA MDFI WASA type ACP DK1 250 W3 0.9 cool downto −16 ° C. 250 W5 0.9 250  W5* 1.2 250 W6 1.1 250 W7 1.1 250 W8 0.4 250 W8* 1.0 DK1/RME (90/10) 250 W1 0.5 cool down to −16° C. 250 W3 2.1 250W5 0.7 250 W6 0.5 250 W7 0 250 W8 0.5

From Table 3 it is obvious that the products of the invention, W5 to W8show similar performances in B0 DK1 as the comparative examples.Moreover W8 even shows better efficiency than W1-3. Even highermolecular weight WASAs, W5* and W8* (M_(n) around 24000 g/mol), showvery good anti-settling performance.

In blends made of DK1 and 10% of RME, the WASA of the invention displaysame performance as EDTA-based reference, and interestingly, all newWASA outperform the comparative example W3 (alpha-olefin-based).

TABLE 4 ΔCP of B0 and B10 DK2 treated with WASA comparative examples (W1to W4) and invention products (W5 to W8). WASA component with * haveM_(n) around 24000 g/mol. Fuel type EVA MDFI WASA type ΔCP DK2 250 W22.3 cool down to −16° C. 250 W3 3.7 250 W5 2.6 250 W6 2.2 250 W7 2.5 250W8 1.4 DK2/RME (90/10) 250 W1 2.4 cool down to −16° C. 250 W2 3.9 250 W34.5 250 W4 5.5 250 W7 1.2 250 W8 1.0 250  W8* 2.3

In Table 4 are displayed the ΔCP values obtained during thesedimentation tests in fuel DK2 and blend thereof with 10% RME. In B0,products of the invention show ΔCP values between 2.2° C. and 2.8° C.which is comparable to the performance obtained using comparativeexamples W2 and W3 with 2.3° C. and 3.7° C. respectively. In this typeof fuel, W8 provides the best wax stabilization as ΔCP of 1.4° C. wasmeasured.

In B10 RME, W1 to W4 show very poor efficiency without exceptions. It isinteresting to notice that the reference WASA W4 differs from theinventive examples as it does not possess N-dispersant functionality. Onthe contrary, inventive WASA W7, W8 and W8* display much better ΔCPvalues of 1.2 and 1.0° C. for number molecular weight of 5000 g/mol andof 2.3° C. for 24000 g/mol.

TABLE 5 ΔCP of B0 and B10 DK3 treated with WASA comparative examples(W1, W3 and W4) and invention products (W5 to W8). WASA component with *have M_(n) around 24000 g/mol Fuel type EVA MDFI WASA type ΔCP DK3 500W3 5.4 cool down to −11° C. 500 W4 4.1 500 W7 3.2 500 W8 3.5 DK3/RME(90/10) 500 W1 3.0 cool down to −11° C. 500 W3 4.7 500 W4 3.5 500 W7 1.2500 W8 2.4 500  W8* 1.7 DK3/RME (90/10) 500 W1 8.1 cool down to −8 ° C.500 W7 1.2 500 W8 3.2

In DK3 B0, the reference WASA, W3 and W4, display ΔCP of 5.4 and 4.1°C., respectively whereas a neat improvement, on the average, of morethan 1° C. lower was measured when using W7 and W8 (DMAEMA and DMAPMAmrespectively).

Sedimentation tests carried out in RME/DK3 blends at −11° C. show thesame ranking with even more pronounced decrease of the ΔCP values, onthe average, of 2° C. When the same blend is cooled down to −8° C.,again, W7 and W8 clearly outperform the results obtained by using W1(EDTA-based WASA) of more than 5° C.

1. A method for improving the cold flow properties of a fuel oilcomposition, said method comprising mixing a polyalkyl(meth)acrylatewith a fuel oil, wherein said polyalkyl(meth)acrylate comprises monomerunits of: (a) from 0% to 40% by weight of one or more ethylenicallyunsaturated ester compounds of formula (I)

wherein R is H or CH₃, R¹ represents a linear or branched, saturated orunsaturated alkyl group with 1 to 9 carbon atoms or a cycloalkyl groupwith 3 to 9 carbon atoms, R² and R³ independently represent H or a groupof the formula —COOR′, wherein R′ is H or a linear or branched,saturated or unsaturated alkyl group with 1 to 9 carbon atoms or acycloalkyl group with 3 to 9 carbon atoms, (b) from 20% to 98% by weightof one or more ethylenically unsaturated ester compounds of formula (II)

wherein R is H or CH₃, R⁴ represents a linear or branched, saturated orunsaturated alkyl group with 10 to 22 carbon atoms, R⁵ and R⁶independently represent H or a group of the formula —COOR″, wherein R″is H or a linear or branched, saturated or unsaturated alkyl group with10 to 22 carbon atoms, (c) from 0% to 10% by weight of one or moreethylenically unsaturated ester compounds of formula (III)

wherein R is H or CH₃, R⁷ represents a linear or branched, saturated orunsaturated alkyl group with 23 to 40 carbon atoms, R⁸ and R⁹independently represent H or a group of the formula —COOR′″ wherein R′″is H or a linear or branched, saturated or unsaturated alkyl group with23 to 40 carbon atoms, (d) from 0% to 30% by weight of vinyl aromaticmonomers, and (e) from 2% to 80% by weight of at least one N-dispersantmonomer, wherein components (a) to (e) add up to 100% by weight.
 2. Themethod according to claim 1, wherein the polyalkyl(meth)acrylate has anumber average molecular weight M_(n) of from 2500 to
 100000. 3. Themethod according to claim 1, wherein the polyalkyl(meth)acrylate has anumber average molecular weight M_(n) of from 4000 to
 20000. 4. Themethod according to claim 1, wherein the polydispersity M_(w)/M_(n) ofthe polyalkyl(meth)acrylate is from 1 to
 8. 5. The method according toclaim 1, wherein the polydispersity M_(w)/M_(n) of thepolyalkyl(meth)acrylate is from 1.3 to 2.5.
 6. The method according toclaim 1, wherein there is a positive amount of the vinyl aromaticmonomer (d) which is selected from the group consisting of styrene andsubstituted styrene.
 7. The method according to claim 1, wherein theN-dispersant monomer of component (e) is a monomer of the formula (IV)

wherein R¹⁰, R¹¹ and R¹² independently are H or a linear or branched,saturated or unsaturated alkyl group with from 1 to 5 carbon atoms, andR¹³ is either a group selected from —C(O)—O—R¹⁴, —C(O)—NH—R¹⁴,—C(NR¹⁵)—O—R¹⁴, —C(NR¹⁵)—NH—R¹⁴ and—C(O)—[NH—C₂₋₁₀-alkylene]_(x)-NR¹⁶R¹⁷, wherein R¹⁵ represents a linearor branched, saturated or unsaturated alkyl group with from 1 to 5carbon atoms or an aryl group, and R¹⁴ represents a linear or branchedalkyl group with 1 to 20 carbon atoms which is unsubstituted orsubstituted by a group —NR¹⁶R¹⁷, wherein R¹⁶ and R¹⁷ independentlyrepresent H or a linear or branched alkyl group with 1 to 8 carbonatoms, or wherein R¹⁶ and R¹⁷ are part of a 4- to 8-membered saturatedor unsaturated ring comprising optionally one or more hetero atomschosen from the group consisting of nitrogen, oxygen and sulphur,wherein said ring may be further substituted with alkyl or aryl groups,and x represents a number 1, 2, 3 or 4, or R¹³ is a group —NR¹⁸R¹⁹,wherein R¹⁸ and R¹⁹ are part of a 4- to 8-membered saturated orunsaturated ring, comprising at least one carbon atom as part of thering which forms a double bond to a hetero atom chosen from the groupconsisting of nitrogen, oxygen and sulphur, wherein said ring may befurther substituted with alkyl or aryl groups.
 8. The method accordingto claim 1, wherein the N-dispersant monomer of component (e) isselected from the group consisting of vinyl substituted nitrogenheterocyclic monomers, N-vinyl-substituted nitrogen heterocyclicmonomers, dialkylaminoalkyl acrylate, dialkylaminoalkyl methacrylatemonomers, methacrylamide monomers, N-tertiary alkyl acrylamides andcorresponding methacrylamides, vinyl substituted amines and N-vinyllactams.
 9. A method for improving the cold flow properties of a fueloil composition, said method comprising: mixing a concentrationcomposition with a fuel oil, wherein said concentrate compositioncomprises (A) from 30% to 90% by weight of a polyalkyl(meth)acrylatewhich comprises monomer units of: (a) from 0% to 40% by weight of one ormore ethylenically unsaturated ester compounds of formula (I)

wherein R is H or CH₃, R¹ represents a linear or branched, saturated orunsaturated alkyl group with 1 to 9 carbon atoms or a cycloalkyl groupwith 3 to 9 carbon atoms, R² and R³ independently represent H or a groupof the formula —COOR′, wherein R′ is H or a linear or branched,saturated or unsaturated alkyl group with 1 to 9 carbon atoms or acycloalkyl group with 3 to 9 carbon atoms, (b) from 20% to 98% by weightof one or more ethylenically unsaturated ester compounds of formula (II)

wherein R is H or CH₃, R⁴ represents a linear or branched, saturated orunsaturated alkyl group with 10 to 22 carbon atoms, R⁵ and R⁶independently represent H or a group of the formula —COOR″, wherein R″is H or a linear or branched, saturated or unsaturated alkyl group with10 to 22 carbon atoms, (c) from 0% to 10% by weight of one or moreethylenically unsaturated ester compounds of formula (III)

wherein R is H or CH₃, R⁷ represents a linear or branched, saturated orunsaturated alkyl group with 23 to 40 carbon atoms, R⁸ and R⁹independently represent H or a group of the formula —COOR′″ wherein R′″is H or a linear or branched, saturated or unsaturated alkyl group with23 to 40 carbon atoms, (d) from 0% to 30% by weight vinyl aromaticmonomers, and (e) from 2% to 80% by weight of at least one N-dispersantmonomer, wherein components (a) to (e) add up to 100 weight %; and (B)from 10% to 70% by weight of a hydrocarbon solvent or oil.
 10. A methodfor improving the cold flow properties of a fuel oil composition, themethod comprising: mixing (a) from 0% to 99% by weight of at least onebiofuel oil which is based on fatty acid esters, (b) from 1% to 100% byweight of middle distillates of fossil origin and/or of vegetable and/oranimal origin, which are essentially hydrocarbon mixtures and are freeof fatty acid esters, and (c) the concentrate according to claim
 9. 11.The method according to claim 1, wherein the fuel oil compositionfurther comprises one or more additives selected from the groupconsisting of additional cold flow improvers, dispersants, conductivityimprovers, demulsifiers, defoamers, lubricity additives, antioxidants,cetane number improvers, detergents, dyes, corrosion inhibitors, metaldeactivators, metal passivators and odourants.
 12. The method accordingto claim 2, wherein the fuel oil composition further comprises one ormore additives selected from the group consisting of additional coldflow improvers, dispersants, conductivity improvers, demulsifiers,defoamers, lubricity additives, antioxidants, cetane number improvers,detergents, dyes, corrosion inhibitors, metal deactivators, metalpassivators and odourants.
 13. The method according to claim 7, whereinthe fuel oil composition further comprises one or more additivesselected from the group consisting of additional cold flow improvers,dispersants, conductivity improvers, demulsifiers, defoamers, lubricityadditives, antioxidants, cetane number improvers, detergents, dyes,corrosion inhibitors, metal deactivators, metal passivators andodourants.
 14. The fuel composition according to claim 10 furthercomprising one or more additives selected from the group consisting ofadditional cold flow improvers, dispersants, conductivity improvers,demulsifiers, defoamers, lubricity additives, antioxidants, cetanenumber improvers, detergents, dyes, corrosion inhibitors, metaldeactivators, metal passivators and odourants.
 15. The method accordingto claim 1 wherein the fuel in the fuel oil composition is a middledistillate fuel.
 16. The method according to claim 1 wherein thepolyalkyl(meth)acrylate polymer is a random copolymer, gradientcopolymer, block copolymer and/or graft copolymer.